Abstract. Increased surface warming over the Arctic, triggered by increased greenhouse gas concentrations and feedback processes in the climate system, has been causing a steady decline in sea-ice extent and thickness. With the retreating sea-ice, shipping activity will likely increase in the future driven by economic activity and the potential for realizing time and fuel savings from transiting shorter trade routes. Moreover, over the last decade, the global shipping sector has been subject to regulatory changes, that affect the physicochemical properties of exhaust particles. International regulations aiming to reduce SO_x and particulate matter (PM) emissions, mandate ships to burn fuels with reduced sulfur content or alternatively, use wet scrubbing as exhaust after-treatment when using fuels with sulfur contents exceeding regulatory limits. Compliance measures affect the physicochemical properties of exhaust particles and their cloud condensation nuclei (CCN) activity in different ways, with the potential to have both direct and indirect impacts on atmospheric processes such as the formation and lifetime of clouds. Given the relatively pristine Arctic environment, ship exhaust particle emissions could be a large perturbation to natural baseline Arctic aerosol concentrations. Low-level stratiform mixed-phase clouds cover large areas of the Arctic region and play an important role in the regional energy budget. Results from laboratory marine engine measurements, which investigated the impact of fuel sulfur content (FSC) reduction and wet scrubbing on exhaust particle properties, motivate the use of large eddy simulations to further investigate how such particles may influence the micro- and macrophysical properties of a stratiform mixed-phase cloud case observed during the Arctic Summer Cloud Ocean Study campaign. Simulated enhancements of ship exhaust particles predominantly affected the liquid-phase properties of the cloud and led to a decrease in liquid surface precipitation, increased cloud albedo and increased longwave surface warming. The magnitude of the impact strongly depended on ship exhaust particle concentration, hygroscopicity, and size where the effect of particle size dominated the impact of hygroscopicity. While low FSC exhaust particles were mostly observed to affect cloud properties at exhaust particle concentrations of 1000 cm^-3, exhaust wet scrubbing already led to significant changes at concentrations of 100 cm^-3. Additional simulations with cloud ice water path increased from ≈5.5 g m^-2 to ≈9.3 g m^-2, show more muted responses to ship exhaust perturbations but revealed that exhaust perturbations may even lead to a slight radiative cooling effect depending on the microphysical state of the cloud. The regional impact of shipping activity on Arctic cloud properties may, therefore, strongly depend on ship fuel type, whether ships utilize wet scrubbers, and ambient thermodynamic conditions that determine prevailing cloud properties.

中文翻译：

---

船用燃料法规对北极云和辐射反馈的潜在影响


摘要。由温室气体浓度增加和气候系统反馈过程引发的北极表面变暖加剧，导致海冰范围和厚度稳步下降。随着海冰消退，在经济活动以及通过较短的贸易路线节省时间和燃料的潜力的推动下，未来航运活动可能会增加。此外，在过去十年中，全球航运业一直受到监管变化的影响，影响了废气颗粒的物理化学特性。旨在减少 SO _x 和颗粒物 (PM) 排放的国际法规，要求船舶燃烧硫含量较低的燃料，或者在使用硫含量超过监管限值的燃料时使用湿式洗涤作为废气后处理。合规措施以不同方式影响废气颗粒的物理化学性质及其云凝结核（CCN）活动，可能对大气过程（例如云的形成和寿命）产生直接和间接影响。鉴于相对原始的北极环境，船舶废气颗粒排放可能会对北极自然基线气溶胶浓度产生很大的扰动。低层层状混相云覆盖了北极地区的大片地区，在区域能源预算中发挥着重要作用。 船用发动机实验室测量结果研究了燃料硫含量 (FSC) 降低和湿式洗涤对排气颗粒特性的影响，激发了使用大涡模拟来进一步研究此类颗粒如何影响发动机的微观和宏观物理特性。北极夏季云海研究活动期间观察到的层状混合相云情况。模拟的船舶废气颗粒增强主要影响云的液相特性，导致液体表面降水减少、云反照率增加和长波表面变暖增加。影响的大小很大程度上取决于船舶废气颗粒浓度、吸湿性和尺寸，其中颗粒尺寸的影响在吸湿性的影响中占主导地位。虽然低 FSC 废气颗粒在废气颗粒浓度为 1000 cm ^-3 时主要影响云特性，但废气湿法洗涤在浓度为 100 cm ^-3 时已导致显着变化。云冰水路径从 约 5.5 g m ^-2 增加到约 9.3 g m ^-2 的额外模拟，显示出对船舶排气扰动的更柔和的响应，但表明排气扰动甚至可能导致轻微的辐射冷却效果取决于云的微物理状态。因此，航运活动对北极云特性的区域影响可能在很大程度上取决于船舶燃料类型、船舶是否使用湿式洗涤器以及决定主要云特性的环境热力学条件。